Fluxonium-Based Artificial Molecule with a Tunable Magnetic Moment

Kou, Angela; Smith, W. C.; Vool, Uri; Brierley, Richard; Meier, Hendrik; Frunzio, Luigi; Girvin, S. M.; Glazman, L. I.; Devoret, Michel

doi:10.1103/physrevx.7.031037

Cited by 56 publications

(54 citation statements)

References 37 publications

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“…In the region in-between the flux sweet spots, where the frequency of the qubit is strongly susceptible to flux noise, T 2 is reduced to values in the range of 50 ns, which could be explained by residual flux noise. The corresponding flux noise amplitude A = 30 µΦ 0 is about a factor of three larger than observed in devices using Josephson junction superinductors [71], and it might be due to the longer superinductor loop.…”

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confidence: 74%

Granular aluminium as a superconducting material for high-impedance quantum circuits

et al. 2019

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Superconducting quantum information processing machines are predominantly based on microwave circuits with relatively low characteristic impedance, of about 100 Ohm, and small anharmonicity, which can limit their coherence and logic gate fidelity. A promising alternative are circuits based on so-called superinductors, with characteristic impedances exceeding the resistance quantum RQ = 6.4 kΩ. However, previous implementations of superinductors, consisting of mesoscopic Josephson junction arrays, can introduce unintended nonlinearity or parasitic resonant modes in the qubit vicinity, degrading its coherence. Here we present a fluxonium qubit design using a granular aluminum (grAl) superinductor strip. Granular aluminum is a particularly attractive material, as it self-assembles into an effective junction array with a remarkably high kinetic inductance, and its fabrication can be in-situ integrated with standard aluminum circuit processing. The measured qubit coherence time T R 2 up to 30 µs illustrates the potential of grAl for applications ranging from protected qubit designs to quantum limited amplifiers and detectors. arXiv:1809.10646v1 [cond-mat.supr-con]

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confidence: 74%

Granular aluminium as a superconducting material for high-impedance quantum circuits

et al. 2019

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“…The situation with deconfinement can be treated in different ways. According to [31], there is no true spin-charge separation in the ordered phases, but the spin-charge separation (or deconfinement) can be treated as a driving force in the unconventional phase transitions.…”

Section: The Case Of Antiferromagnets and Discussionmentioning

confidence: 99%

Quantum topological transitions and spinons in metallic ferro- and antiferromagnets

Irkhin

2019

Physics Letters A

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An effective Hamiltonian describing fluctuation effects in the magnetic phases of the Hubbard model in terms of spinon excitations is derived. A comparison of spin-rotational Kotliar-Ruckenstein slave boson and Ribeiro-Wen dopon representations is performed. The quantum transition into the half-metallic ferromagnetic state with vanishing of spin-down Fermi surface is treated as the topological Lifshitz transition in the quasimomentum space. The itinerant-localized magnetism transitions and Mott transition in antiferromagnetic state are considered in the topological context. Related metal-insulator transitions in Heusler alloys are discussed.

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“…This includes a wide variety of superconducting qubits for quantum computation [4][5][6][7][8], quantum-limited microwave amplifiers [9][10][11], and frequency converters for quantum signal routing [12]. These circuits can be probed using standard rf measurement techniques and understood within the theoretical framework of circuit quantum electrodynamics (cQED) [13], which has been used to accurately predict energy levels and intermode coupling strengths in novel and complex circuits [14][15][16]. Arguably the most well-studied quantum circuit is the capacitively shunted Josephson junction [4,7], which is parameterized by the ratio of the Josephson coupling energy E J to the charging energy E C .…”

Section: Introductionmentioning

confidence: 99%

Direct Dispersive Monitoring of Charge Parity in Offset-Charge-Sensitive Transmons

et al. 2019

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A striking characteristic of superconducting circuits is that their eigenspectra and intermode coupling strengths are well predicted by simple Hamiltonians representing combinations of quantum circuit elements. Of particular interest is the Cooper-pair-box Hamiltonian used to describe the eigenspectra of transmon qubits, which can depend strongly on the offset-charge difference across the Josephson element. Notably, this offset-charge dependence can also be observed in the dispersive coupling between an ancillary readout mode and a transmon fabricated in the offset-charge-sensitive (OCS) regime. We utilize this effect to achieve direct, high-fidelity dispersive readout of the joint plasmon and charge-parity state of an OCS transmon, which enables efficient detection of charge fluctuations and nonequilibrium-quasiparticle dynamics. Specifically, we show that additional highfrequency filtering can extend the charge-parity lifetime of our device by two orders of magnitude, resulting in a significantly improved energy relaxation time T1 ∼ 200 µs. arXiv:1903.00113v2 [cond-mat.mes-hall]

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Fluxonium-Based Artificial Molecule with a Tunable Magnetic Moment

Cited by 56 publications

References 37 publications

Granular aluminium as a superconducting material for high-impedance quantum circuits

Granular aluminium as a superconducting material for high-impedance quantum circuits

Quantum topological transitions and spinons in metallic ferro- and antiferromagnets

Direct Dispersive Monitoring of Charge Parity in Offset-Charge-Sensitive Transmons

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